Refrigerant compressor protecting device

Abstract

A protecting device for protecting a refrigerant compressor from overheating or seizure caused by a shortage of refrigerant by any chance such as leakage thereof. The device includes a temperature sensor disposed on the outer wall of the compressor casing in the vicinity of a refrigerant intake suction suction port for sensing the temperature of the outer wall to output the sensed or measured data and a discriminator for discriminating an occurrence of refrigerant shortage by an excess of the data over a predetermined condition for comparison. The signals from the discriminator cause a warning issuance of the refrigerant shortage or an automatic stoppage of the compressor operation.

What is claimed is: 
     
       1. A protecting device for protecting a refrigerant compressor which is connected to a refrigeration circuit containing a refrigerant enclosed therein from overheating problems resulting from a shortage of the refrigerant in the refrigeration circuit, said protecting device comprising; a temperature sensor for sensing the temperature of an outer wall of said compressor in the vicinity of a refrigerant intake suction port and providing an output signal representative of the sensed temperature value;   a discriminator for detecting a shortage of the refrigerant by detecting a temperature value in the output from said temperature sensor which is greater than a set value, and emitting a refrigerant shortage signal when such a shortage is detected; and   protection means for taking action necessary to protect said compressor against such overheating problems resulting from such refrigerant shortage, in response to the signal emitted from said discriminator.   
     
     
       2. A protecting device claimed in claim 1, wherein said protection means is a warning lamp to give an operator a warning of the refrigerant shortage when the the lamp is energized by the signal emitted from said discriminator. 
     
     
       3. A protecting device claimed in claim 1, wherein said protection means is a means for automatically stopping the operation of said compressor. 
     
     
       4. A protecting device claimed in claim 3, wherein said compressor is driven, via a clutch, by an engine of a vehicle and said clutch functions as said protection means by disconnecting said compressor from said engine. 
     
     
       5. A protecting device claimed in claim 3, wherein said compressor is driven by an electric motor and said protection means is means for interrupting power to said electric motor. 
     
     
       6. A protecting device claimed in claim 1, further comprising a delay circuit for delaying the signal from said discriminator by a predetermined time duration which is required from the starting of said compressor to the moment when the temperature of said outer wall of the casing, to which said temperature sensor is attached, is able to come down from a value exceeding said set value of substantially stationary value, whereby said protection means will not become activated immediately after starting of the compressor in spite of sufficient amount of refrigerant being present in said refrigeration circuit. 
     
     
       7. A protecting device claimed in claim 1, wherein said set value is predetermined fixedly and commonly with respect to the magnitude of the refrigerating load applied to said refrigerating circuit. 
     
     
       8. A protecting device claimed in claim 1, wherein said discriminator comprises: load sensing means for sensing the refrigerating load to said refrigerating circuit;   calculating means for calculating said set value from an equation which represents the relation between a refrigerating load, at the time when the amount of the refrigerant is at the critical level at which the compressor is desired to be stopped, and a temperature of the outer wall of the casing at a position where said temperature sensor is attached; and   a comparator for comparing said set value and the temperature measured by said temperature sensor and emitting the refrigerant shortage signal when the measured temperature exceeds said set value.   
     
     
       9. A protecting device claimed in claim 8, wherein said load sensing means is a sensor for sensing the degree of opening of an expansion valve in said refrigerating circuit. 
     
     
       10. A protecting device claimed in claim 1, wherein said compressor is a swash-plate type compressor which comprises a casing having said outer wall, a plurality of pistons reciprocatively disposed in said casing and a rotating swash-plate for actuating said pistons, and said refrigerant intake suction port is disposed on the top of said casing symmetrically with a refrigerant discharging port in relation to the axis of said casing. 
     
     
       11. A protecting device claimed in claim 1, wherein said temperature sensor is located at an area within a circle of radius 4D from the center of said refrigerant intake suction port, D being the diameter of said intake suction port. 
     
     
       12. A protecting device claimed in claim 11, wherein said temperature sensor is attached to a flange of a suction pipe fixed to said casing in the vicinity of said refrigerant intake suction port.